Chase Log: July 17th, 2018 Alta Vista, KS Tornado?

An impromptu chase in mid-summer rewarded me with a decent supercell that may or may not have produced a tornado.

July 17th was a pretty average summer day, with modest northwest flow aloft and a strongly veered (but weak) wind profile. An outflow boundary was present over the Flint Hills, but was moving southward. You want outflow boundaries to be about stationary for maximum effect, but I still was keeping an eye on mesoanalysis and radar. A couple storms developed near Manhattan, and another one popped up east of Junction City. It looked like junk on KTWX (Alma, KS radar site) but when I checked the Wichita radar it looked much more interesting. I decided to head west on I-70 towards it around 4:40 pm.

Sure enough, as I was heading west, I noticed it was starting to develop a telltale supercell shape. I should have left a bit earlier. I got off I-70 at the Alma exit in Wabaunsee County and headed south on K-99 and then west on K-4 towards Alta Vista. I got off the highway a few miles east of Alta Vista and headed southwards on gravel roads until I could find a good position.IMG_0610.CR2.jpg

5:42 pm, a few miles southeast of Alta Vista. Although structure isn’t great, a big inflow tail is visible on the right side of the photo. I was keeping an eye on the center of the photo, where the inflow tail is feeding into the storm. I crept west a bit on the road for a slightly closer look.IMG_0611.CR2.jpg

5:45 pm, a bit west of previous photo. A Rear-flanking downdraft cut is starting to show itself here in the center. I was starting to wonder if this storm was going to try to produce a tornado. As I was driving west and then south, a suspicious lowering appeared where I would expect a tornado in relation to the RFD cut. I stopped twice to look at it, but it appeared to just be scud rising into the base of the storm. I found a good stopping point to take some photos.IMG_0613.CR2(1).jpg

5:53 pm, six miles southeast of Alta Vista, looking WNW. The image is slightly color-enhanced to help with contrast. There is a bit of a lowered area in the center on the NW side of the RFD cut, right where a tornado usually would be. There appeared to be “scud” filaments rising into the feature. The feature persisted for approximately 3 to 4 minutes. If it was a tornado, it was likely very weak. I wasn’t completely sure what was going on, so I didn’t send a report to the NWS about it. Later as I checked my photos, I sent a report to the NWS via Twitter about my experience, explaining that I still didn’t know what that was. As of this writing, no tornado has been confirmed yet.

After the feature dissipated, the storm transitioned into an outflow-dominant state. I continued south and east some more to find a good spot.IMG_0616.CR2.jpg

6:10 pm, southeast of Alta Vista, looking NW. There is still somewhat of an RFD cut visible, but I was getting NW winds at this time. I was beginning to wonder if the storm had become elevated, as the outflow boundary was 10 or so miles south of the storm by this point. It appeared to try to bring in surface or near surface based inflow one more time, then started to dissipate.IMG_0620.CR2.jpg

6:26 pm, southeast of Alta Vista, looking east. A couple of nice rainbows ended a very interesting day in the Flint Hills.

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